The thalamic reticular nucleus (TRN) is believed to play an important role in cognition by modulating the sensory information destined for cerebral cortex. This gating of sensory information appears fundamental to the normal processes of maintaining attention and generating waveform activity characteristic of sleep. Abnormalities of the TRN, or regions of the brain that project to the TRN, are implicated in a number of neuropathological conditions. Such conditions include attention deficit disorders, absence (petit mal) epilepsy, and Alzheimer's disease. Crucial data regarding the TRN are limited and many fundamental questions remain unresolved. We propose to use complementary neuroanatomical and electrophysiological methods to thoroughly analyze the visual sector of the TRN in Galago crassicaudatus. The data obtained from the proposed studies will significantly advance our understanding of the role of the TRN in normal and pathological conditions.